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A miniature rocket device integrating nanothermite and RDX is presented for shock initiation of high explosive application. This Ø 2.5 mm device consists in several assembled and screwed parts: a pyroMEMS chip with a Al/CuO multilayers on it to ignite within less than 100 μs a few milligrams of nanothermite, which reacts violently and ignites within 150 μs a RDX charge compacted in the closed combustion chamber. The gases generated by the RDX combustion rapidly expand, cut and propel a Ø 2.5 mm by 1 mm thick stainless steel flyer in the barrel. After the presentation of the rocket design, fabrication and assembly, by measuring the pressure‐time evolution in the chamber we demonstrate the advantage to ignite the RDX with Al/Bi2O3 nanothermite to optimize the pressure impulse. We show that the stainless steel flyer of 40 mg is properly cut and propelled at velocities calculated from 665 to 1083 m s−1 as a function of the RDX extent of compaction and ignition charge. As expected, the average flyer velocity increases with the mass of loaded RDX and flyer's shear thickness. We finally prove that the impact of the flyer can initiate directly in detonation a RDX explosive, which is very promising to remove primary explosives in detonator.

[a] 1I ntroductionAlumino-thermite materials represent an interesting class of energetic substances notably because of their high energy densities, adiabatic flame temperature, and when nanosized, high reaction rates. Alumino-thermite is an oxidation-reduction reaction involving am etal (fuel) and am etallic oxide (or possibly an on-metallic oxide) that forms as table product after reaction.Thermite materials have been actively investigated for aw ide range of potential applications including railroad welding, materials processing to form refractory materials, additives in propellants, explosives and pyrotechnics [1][2][3], and more recently also for micro initiation [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20],e nvironmentally clean primers, and in situ welding [21].Among the numerous possible exothermic metal/oxide pairs listed in the literature [22],t he most investigated ones mix Al with MoO 3 ,C uO, Bi 2 O 3 ,F e 2 O 3 ,M nO 2 ,W O 3 ,a nd I 2 O 5 .F or the last two decades most of the research efforts aimed at reducing metal and oxide components size, improving their intimacy,t oi ncrease the reaction rate and decrease the ignition delay while improving safety.More recently,t hermite materials were also considered to produce gas species or pressure bursts, opening new potential fields of application such as pressure mediated molecular delivery [23,24],b iological agent inactivation [25][26][27],h ydrogen production [28,29],o rp ropulsion systems [7][8][9].Af ew teams demonstrated experimentally that Al/Bi 2 O 3 and, to al esser extent, Al/I 2 O 5 mixtures generate the highest pressure pulses [27,30,31] in comparison with other thermites. Martirosyan [31] considered that the reaction product (bismuth or iodine) boils at at emperature of 1560 8Ca nd 184 8C, respectively,w hich is lower than the maximum reaction temperature:t herefore causing bismuth or iodine evaporation with subsequent increase of the released gas pressure.For some thermites, such as Al/CuO, experiments using time-resolved mass spectrometry have measured significant O 2 release under rapid heating [32,33].T he formation of gaseous intermediates and their contribution to the pressurization may suggest why as ystem such as Al/MoO 3 , which is thermodynamically predicted to produce approximately only ap ercent of the gas that Al/CuO or Al/Bi 2 O 3 does, reacts rapidly and generates pressure as many other thermites.Despite these experimental research investigations, the effects of thermite composition, packing density together with its environmental conditions on the gas production (type and repartition of produced species and rate of gas release) need to be studied and understood in greater detail. On the theoretical side, af irst attempt to simulate Abstract:T he paper proposes an ew theoretical model based on local thermodynamic equilibrium enabling the prediction of gas generation during the reaction of aluminum-based thermites. We demonstrate that the model has the capability to predict the total pressure and the partial p...

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